Override Config of Django app, extra django-cms migration is created

Oct. 31, 2021, 6:55 a.m.

Sometimes you need to override Config for various reasons.

For example, in my case, after updating django 3.2+, a migration for django-cms was automatically created when you call makemigrations for your project.

It was in this error that this behavior arose due to the introduction of default_auto_field (see: https://docs.djangoproject.com/en/3.2/ref/applications/#django.apps.AppConfig.default_auto_field) and setting your DEFAULT_AUTO_FIELD to a value other than django.db.models.AutoField, namely django.db.models.BigAutoField. Therefore, when calling makemigrations, a migration was created in which the type of the ID field became BigAutoField for all django-cms models.

To fix the error above, you need to override CMSConfig in any of your applications in any file, but for convention it is better in apps.py:

# spec/apps.py
from cms.apps import CMSConfig as BaseCMSConfig

class CMSConfig(BaseCMSConfig):
    default_auto_field = 'django.db.models.AutoField'

Now replace 'cms' in INSTALLED_APPS:

    # 'cms',

If you have already run migrate in your project, then you need to return the correct type to the ID fields. To do this, run makemigrations so that the ID field become django.db.models.AutoField again, and apply the migration with the migrate command. Now you can already delete the last two migrations from your project. It is also possible to delete records of applied migrations from the database (although this is not essential).

I think the django-cms developers will add default_auto_field by default, so in your project after updating the django-cms version, check if default_auto_field appears in CMSConfig. If so, return 'cms' to INSTALLED_APPS.

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Author of Article

Artem Maltsev

Web-developer, having the knowlenge of programming language - Python, framework - Django, content management system - Django CMS, platform of e-commerce site - Django Shop and many other applications, using this technologies.

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